package com.smartbone.pagination;

import javax.faces.model.DataModel;

@SuppressWarnings("rawtypes")
public abstract class PagedListDataModel extends DataModel {
    int pageSize;
    int rowIndex;
    DataPage page;

    /**
     * Create a datamodel that pages through the data showing the specified
     * number of rows on each page.
     */
    public PagedListDataModel(int pageSize) {
        super();
        this.pageSize = pageSize;
        this.rowIndex = -1;
        this.page = null;
    }

    /**
     * Not used in this class; data is fetched via a callback to the fetchData
     * method rather than by explicitly assigning a list.
     */
    public void setWrappedData(Object o) {
        if (o instanceof DataPage) {
            this.page = (DataPage) o;
        } else {
            throw new UnsupportedOperationException(" setWrappedData ");
        }
    }

    public int getRowIndex() {
        return rowIndex;
    }

    /**
     * Specify what the "current row" within the dataset is. Note that the
     * UIData component will repeatedly call this method followed by getRowData
     * to obtain the objects to render in the table.
     */
    public void setRowIndex(int index) {
        rowIndex = index;
    }

    /**
     * Return the total number of rows of data available (not just the number of
     * rows in the current page!).
     */
    public int getRowCount() {
        return getPage().getDatasetSize();
    }

    /**
     * Return a DataPage object; if one is not currently available then fetch
     * one. Note that this doesn't ensure that the datapage returned includes
     * the current rowIndex row; see getRowData.
     */
    private DataPage getPage() {
        if (page != null) {
            return page;
        }
        int rowIndex = getRowIndex();
        int startRow = rowIndex;
        if (rowIndex == -1) {
            // even when no row is selected, we still need a page
            // object so that we know the amount of data available.
            startRow = 0;
        } // invoke method on enclosing class
        page = fetchPage(startRow, pageSize);
        return page;
    }

    /**
     * Return the object corresponding to the current rowIndex. If the DataPage
     * object currently cached doesn't include that index then fetchPage is
     * called to retrieve the appropriate page.
     */
    public Object getRowData() {
        if (rowIndex < 0) {
            throw new IllegalArgumentException(
                    " Invalid rowIndex for PagedListDataModel; not within page ");
        } // ensure page exists; if rowIndex is beyond dataset size, then
        // we should still get back a DataPage object with the dataset size
        // in it
        if (page == null) {
            page = fetchPage(rowIndex, pageSize);
        }
        int datasetSize = page.getDatasetSize();
        int startRow = page.getStartRow();
        int nRows = page.getData().size();
        int endRow = startRow + nRows;
        if (rowIndex >= datasetSize) {
            throw new IllegalArgumentException(" Invalid rowIndex ");
        }
        if (rowIndex < startRow) {
            page = fetchPage(rowIndex, pageSize);
            startRow = page.getStartRow();
        } else if (rowIndex >= endRow) {
            page = fetchPage(rowIndex, pageSize);
            startRow = page.getStartRow();
        }
        return page.getData().get(rowIndex - startRow);
    }

    public Object getWrappedData() {
        return page.getData();
    }

    /**
     * Return true if the rowIndex value is currently set to a value that
     * matches some element in the dataset. Note that it may match a row that is
     * not in the currently cached DataPage; if so then when getRowData is
     * called the required DataPage will be fetched by calling fetchData.
     */
    public boolean isRowAvailable() {
        DataPage page = getPage();
        if (page == null) {
            return false;
        }
        int rowIndex = getRowIndex();
        if (rowIndex < 0) {
            return false;
        } else if (rowIndex >= page.getDatasetSize()) {
            return false;
        } else {
            return true;
        }
    }

    /**
     * Method which must be implemented in cooperation with the managed bean
     * class to fetch data on demand.
     */
    public abstract DataPage fetchPage(int startRow, int pageSize);

    /**
     * 进行删除等操作后会立即改变列表项并且返回列表页的，请调用此方法，用于刷新列表。
     */
    public void refresh() {
        if (this.page != null) {
            this.page = null;
            getPage();
        }
    }
}

